Telephone system



Nov. 30 1926. 1,608,488 v l.. J. BowNraI TELEPHONE SYSTEM Filed May 9. 1924 2 Sheets-Sheet 1 E uw LOW RSITANCE X 'TURNS maf/mez if 9 x rumvs m2 VY' HIGH by my Nov. 3o, 1928. 1,608,488

l y L. J. BOWN E TELEPHONE SYSTEM Patented Non'. 30, 1926. y

nANGEQRD cLexion/"1in, or argwaan nniicnniiivfyoR-K,lassienonTo Wiesmann nene Turc ,eQMrvaNYwnooaeogeapren, or new IYYQRK; n? Y., AA eonronafrron" on 'NEW YORK ,a y y t Y QrnLEPHoNn sYs'rEM.

Application filed May 9,1924. Serial No. 71.5248,

:This invention relates to. telephone systemsycity inwhich ease aseeond trunk line loadand more particularlyfto trunk circuits for H ing tojt'bis exchange and 'a vsecond socalled B extending. telephone connectionsl between operator are,involved.` In the lirst instance, automatic telephone exchanges and inanualyftlle battery ony the'iilineninay only `be lintertelephoneexchanges. Qrlipted once,namely, :whenl thelconnecvtion In systems of ,this type it is oftenldesir* is extended bytheinwardoperator to the zableto extendconnectionsfrom a subscriber JWantecl sulbscriber,l ivhereaa. inthe second inone city, to .a subscriber-rin theinain ex#-instance,the Abatterywmay be interrupted change .oftaiiothercityl or to a subscriber,twice; i. `e once whenV they connectionl is .-'locatedfeitheninanotherfexchangel in that extended byfthe inward operator and a secondrcity or', in i anexchange in a third second tiinewwhen it is extended byA the B city: To tliis,end,trunlrs are provided ben, operatoras isY )vellglrnoivn in theart. tween the automatic exchange' and a manual It isan object, therefore, of this invention tolleXchange, inV the first cityjfrom =-which tof', provide a trunk. circuitJ for use in `the @these various connections may be made by above type ojtfeautomatic to manual connecthe aid of a so-called tandem toll or twotions, that is equipped with means ivherehy number7 operator, the expressionfftwo-numthe essentialsignal indications are estabber? indicating: that ,tivo numbersv are in-lished and function in a-unifgorni manner volved in .setting ugthe connection, i. e., one Vregardle.ss of the nature of the connections number, for the ,diStant-cityand alsecondn` established beyond; i. ef, Whether such conone ,for .thesubscriber in that cityghfSuchL:nections"*extendithrough one oreinore eX- trunlrsfmust, of, necessity, beprovided Ywith changes;andwinvolvekthe use of one or more means whereby disturbances, incident tothe operators 'and corr:esponding` trunk lines. fsetting up of the connection through these Another object is the `n:rovisio'n.oa trunk variousexchanges, vWill` not in any Way alf-4A circuit of `this type haying means yfor `tranvifect the proper functioning of the circuits; `mittinmg the usual signal indications essential yi. e.,jtor example, any temporary disconnec-.mto tl'iehproper supervision oi", thebonnection Vtion inthe battery mustk'not interterey'ith or Moneit-lier'iside of the trunk circuit. cause the falseoperation of supervisory sig To attaintheseobjects, in accordance with `nals `'such as ,busy backsignals, busytmeah one feature of thei invention, means are ringing' signals` disconnect signals,flashing `provided inthis trunlrlhcircuit' Wherebm recall signals, etc;` Trunks of this sortdlead.- g after thenusualdine and auxiliary signals ing from an automatic exchange to a manare lighted, when: the trunk is seized and ual `toll''exchange d0 notdepend forltheir se i extinguished when the listening key is operi lection on the luse ofsocalledicall Wire servicedatcdy` theylineY lamp "alone is again lighted but ,are,usually;automatically selected by a as aguard signalwivhe'n the'listenjinq' he] switch in the automaticexchangeuthat picks is released and remains lighted until Vthe out the iirst idletrunk.;v `This trunk is idcntandem voperator, inserts. the plug` of this tified at Athe toll exchange by the `lifting?!trunleintoV an Voutggioing1f trunliline jack. 40'. of a signal lampgu'hichindicates to thetan i, rrnotherz feature iswthe provision, in this y. demoperator that athroug connection is trunk'rciifcuit; of means .whereby signal desired: Thef tandemA operrtoigllupon, reg isfopeed nofyingruthetandem operator e ceivingsuch a signala4 connects her ntelephmie that the connection beyond has been c o aset to the seized trunk and afterhaying pleted tothe Wantedsubscribers line and received. the details oi' the'vcall. from the soiy V,that thedringing'operations mayybegin. This calledinachine switching A operator at" the l ringing signalis operated thelinfoinentstead;7 l automatic exchange, proceeds Withthe setl-battery suppliedt fthetrunlrcircuitwhen .ting up of the connection. it is-connected ,directly tothe subscribers As stated. the `Wanted subscriber may be line by the aid of but afsingle Vtrunk line located in the main exchange in adistant and operator at 51599011@ GXCheDg, 'LS "VGN city which involves the, use of but a single asfvyhen the connection iscoinhleted through trunlr lineAleading' thereto and a so-called` n inward operator thereator the subscriber v.may helccatel in a exchange in tlmt g additional exchanges with the aid additionally .trunlr l lines and `op;erators regardless o tif fl'faet the `n uh the eminectinns vthe ringing signal 1s maintained through each. of these exchanges an impulse of battery is momentarily supplied. A timing and counting relay arrangement is provided so that this ringing signal will not operate on such impulses but will function only at the proper time, i. e., when a steady 'supply of battery is finally supplied.

Another feature is the provision of means in the trunk circuit whereby code ringing may be effected upon the operation of a ringing key according to a certain code, whereby a ringing tone isv simultaneously transmitted to the machine switching operator or the calling subscriber and whereby operated during the ringing period.

Another feature is the. provision of means whereby the ringing signal is extinguished by the function of the timing relay arrangement when the ringing key is finally released after the sending of code signals providec the subscriber has answered in the meantime by removing his receiver from the hook, whereas if the subscriber has not answered and the key is released, the signal is not extinguished.

Another feature is the provision, of means whereby, when a called subscriber answers, and the ringing signal isextinguished, relays in the trunk circuit are operated to cause the actuation of supervisory signals at the machine switching operators position as an indication that connection to the wanted subscriber has been completed.

Another feature is the provision of means whereby busy back signals may be transmitted through the trunk circuit to the machine switching operators position without operating the ringing signals; i. e., the busy back pulses are of such duration and the interval between them is such that the counting and timing relay arrangement prevents the first two impulses from being transmitted as busy back signals, as disturbances caused by the manner of extending the connections beyond may be similar to t-hese two first signals. l

Another feature is the provision of means whereby the called subscriber may flash signals at the machine switching operators position without lighting the ringing signal or causing any other disturbances in the trunk circuit.

Another feature is the provision of means 4 in the trunk circuit for calling the tandem operator before the. called subscriber has answered by the flashing of the line and auxiliary signals without operating a discount signal.

Another feature is the provision of means in the trunk circuit whereby the disconnect signal is lighted the moment the trunk is released at the machine switching operators position, and the plug of the trunk is still connected to the jack of the outgoing line,

and whereby the simultaneous operation of a relay causesV a disconnect signal to be sent through the outgoing trunk line to the distant operators position.

Another feature is the provision of means whereby the line and auxiliary signals are lighted after the trunk is seized a second time before the connection beyond of a previous call has been taken down while the disconnect signal, which was lighted as a signal to disconnect this previous connection, remains lighted until the tandem operator has removed the plug from the outgoing trunk line jack.

The invention may be described inconnection with the accompanying drawing in which Fig. 1 illustrates at an automatic exchange, a subscribers line and automatic and manual connecting switches therefor to a machine switching operators (ord circuit; an automatic selector switch and that portion of a two-number trunlr which is vlocated at the automatic exchange and terminates at this switch. Fig. 2 illustrates a manual toll exchange and the end of the two-number trunk terminating at a tandem toll roperators position. rlhis figure also illustrates, in diagrammatic'form, to the right of the dotted vertical line a main exchange and an inward, operators position thereat and a trunk line leading from this exchange to another exchange at which a B operator is located; also below the dotted horizontal line a trunk leading from the manual toll exchange to a combination inward` and B operator at another city.

vReferring to Fig. 1, a connect-ion from the machine switching operator A to the calling subscribers line 10 is indicated diagrammatically and this connection may be made over a. line finder LF, a selector S lines of which terminate at a ack such as J in front of the machine switching operators cords such as A the plug of which may be connected to this jack J. rl`he machine switching' operator receives the details of a call from the subscriber at 10 and causes, through mea-ns well known in the art, the operation of the switchQO to select an idle outgoing two-number trunk T over conductors 30 leading to a manual toll exchange and ending into a plug at a tandem toll operators position TO. From this manual toll exchange connectionvmay be made to various points such as, for example, through jack to a main exchange located at another city` which for the sake of convenience will he called Providence, and from there. directly to a subscriber 161 by means of the plug 162 and jack 163 of the inward operator 10 or by means of jack 164 to another exchange 165 in the same city where an operator BQ may extend the connection to a subscriber 166 .in this exchange by means of plug 16T and jack 168. On the other hand, a connec- .tion maybe extended from the ,tandem toll operator TOv by meansof a jack-170`lto an exchange 1T1'in another eityfsuch as Providenceyand froml Athere by ,meansof a coinbina-tien inward'zunjl B operatorl() to a subscriber 172 luy-means of plug;yr 173 and jack 1741.

This invention Imay be more readily understoed iff the functions ci' theftrunli circuitI T are described in `theestablish-ing of a connection between a subscriber, 10 and a subscriber-at a diet-ant city. It Will be sufficient to consider that, in accordance With Well known methods employed in automatic telcphony, theline of the `subscriber at 1.0 has beenjconneeted to the machine switching eperators cord circuit et position A and that this operator has Vcaused' the switchl 20 Ste connect the cord circuit to a' toll trunl T.

The firstoperation, therefore, inthe trunk circuit T upon completion ot thie 'coi'ineetion ie, the vclosing of a circuit'through the tip and ring brushes 17 and 18 and corresponding terminals 1Gand 19 of the trunk "ll from ground through a high Voltar battery, resistance 11, armature. und baci; Contact oi" rel-ay 12, ,Winding of relay 13,' left hand Winding' ot relay 14upper left handwiuding` oftherepeating coil 15, terminel' 113 and brush 1 7 through a relay 9 bridged across; theftip and ring conductors or the cord circuit, brush 18, terminal 19, `lower `lett hand Winding of repeatingcoil 15, 'right'hand Windingof relay 141- through a lou* voltage battery back to` ground. :Since the two windings of relay '1'1- Aare in series in 'this circuit, the 'same amountof current must flow through each and since both windings have the same number of turns, the` meg;- netic effect will be the same' in each. Due then to the direc-tion of the windings these magnetic eiiectslare equal and opposite and the net result is nil and relay 14. therefore remains unoperated'. Relay 13, l also ineluded. in this circuitoperatee und causes in turn the, operation of relay 21 over en obvious circuit. `Relay 21 in operating short`- circuits the Windingoi relay 1?,-v by a cir cuit through its outer lett hund arniuture and liront Contact. Relay 13 releases; openingl the operating circi'iits "te-r relay 21, which however, is nouv held' up .at its own outer left hand armature and front Contact to the sleeve terminal andbrush 2in' to a ground at the machine switching' operators cord circuit. 'Relay 21 also closes atits outer right hand armature, an obvious cir cuit for relay 27 causing this relay to operate und close et its `armature and front cone tact an obvious circuit `tor the operation of relay 12. Relay 12 in operating opens the operating circuit for relay 13 at its arma ture and back Contact and prevents `relay 13 from operatino again until the ground en the sleeve lea( at brushi26 is removed and lower lett hand Winding` ot'iepeutu relays 21, 27 and 12 are thereby released. Relayl further closes n circuit for the `high ifoltag'e 4battery through vthe Winding' offrelayI 28,*inner `left hand armature und front contectuot relay 21, `resistance 29, outer leift hand 1armature und bueh Contact of reley ljlowerright hand winding" ot repeating'iieoilfl,i ring conductor o trunk T, louter left hand Winding of repeating,Y eoil 175', resistance101, inner right hand armature and beclfcontact olf ,relay 102to a point 103'and-also a peral-lelcircuit from ;-coil 175 throughleft handwinding' otpolerizet. relay 104- to thisl pointwlll end frein this point to the right hand "Winding loi relay 105,"letfh and armature 'und beek 'contact of relay 102 upper left hand'n'indin; repeating coil 175, the tip conductor et trunk lll, upper righthund Windingoi'' repeating` coil 15, right hand armature und bach ccntafctof relay 31, resistance "2 lto ground.

als.; `lfhe high voltage better-y at relay 28 Cena-ies the operation ot relays 28 and 105.*Whereus relay 10e'L y@loes not operate at 'this time. Reley'f28, in operating, connects a ground at its armuture end front contee `ut the louv voltager battery side of resistance 11. `which `Allround reverses the flow of current inthe circuit through the bridged relay 9 in the cord circuit.4 The relay 1:' does not operate on this reversal" the relation oi the winding-e thereof lremain the same. `This reversal"ceuseschengee to tate place in the cord 4circuit et A to prepare it for supervisione which, however, are outside ot' the s'cepe` oi this `invention and maybe ot `any standard type 1Well known in the art 'telephonyL for 'notifying -ithe trunk line? has been rseized etc.

Relay 105 in operatingv closes un ebvioue circuit for relay 106 which in energ'zingr closes a circuit tor the auxiliary off operator that Vlamp 108 and'line lunip 100 as loller-fe:

Batteryline lamp 109, outer right band armature :und bach coutent o? rilai' 1,10,

'armature und-iront Contact ofi' relay 100;

inner right hand ii'ialie-l'iefcredireel: coutaets ot' relay 110, auxiliary leuip 108"to ground. The lighting` o-i' these lamps neties the tandem'operator at 'F0 that trunk T has been Seized `und that?, through connect-ion is desired.

rllhe tandem operator now de'iresees listening' key 112 thereby bridging' her 'telephone set at 113 icross the tip and ring conductore 50 of trunlT through the repeating' oeil 1175 und right hund windings of repeating coil 15., and is thus placed in position to obtain the information from the machine switching operator at- A for the passing of the. call. The operation of the auxiliary contacts 115 of listening` hey 112 causes relay1 110 to operate from battery Winding of relay 110,

inner left hand armature and back contact of relay 110, contacts 115, armature and front Contact of relay 106, inner right hand malte-before-break contacts of relay 110, lamp 103 to ground. The closing of contacts at 131 of the listening key and operation of relay 110 prepares a circuit for relay 116 from battery winding cf relay 116 left hand make-before-breal; contacts of relay 116 contacts 131, outer left hand armature .and front contact of relay 110 armature and back Contact of relay 104 to ground at the lower armature and back Contact of relay 132. The operation of relays 110 and 116 causes locking circuits for themselves as follows: relay 110 directly to ground at its inner left hand malte-beforebreak contacts, armature and front contact of relay 106 and inner right hand armature and front contact of relay 110 to ground whereas relay 116 locks to the same ground through its left hand armature and front contact and outer left hand connection and back contact of relay 137. rThe operation of relay 110 therefore extinguishes the auxiliary signal lamp 108 by the breaking of the inner right hand inalre-beforabrealr contacts thereof while the line lamp 109 is eX- tinguished by Ithe opening of the outer right hand armature. and back Contact. The operation of relay 116 opens at its outer right hand armature and back contact, a circuit forrelay 102 to prevent false operation of this relay on the setting up of the connection as will hereinafter be described. Belay 116 also closes at its inner right hand armature and front contact, a starting circuit to the front contact and armature of the pulsing relay 126 for the operation of the counting relays 120, 121. 122, 123 and timing relays 124 and 125, These counting and timing relays will now be used to distinguish between the various supervisory signals that will be received from the circuits beyond, such as busy back signal pulses interruptions in the battery supply due to the manner of extending the connection and steady battery connections which denote that the circuit is completed to a Wanted subscribers line as will hereinafter be described.

1f the tandem toll operator the information for passing on the call, and releases her listening lrey the line lamp is again lighted as a guard signal to indicate this condition. The circuit for the lamp is as follows: battery, lamp 109, normal auxiliary contacts at 131 of listening key 112, outer-left hand armature and front contact of relay 110, armature and back contact of relay 104, lower armature and bacl: contact of relay 132 to ground.

The tandem toll operator is, therefore, now ready to insert plufr 140 of trunk T into either j ack 150 or 170 depending on whether a call is intended for the main exchange 160 now receives neoaass in the town of Providence or for an eX- change 171 in the town of Worcester. It will be assumed that a called subscriber is located in Providence and, therefore, after having a trunk line assigned and the usual busy. test performed on the sleeve on the jack 150 of this trunk line leading to main exchange. 160, the tandem toll operator inserts the plug 140 into jack 150. Relay 133 operates. from battery resistance 134, left hand winding cf relay 133, right hand armature and back cont-act of relay 135, slee-ves of plug 140 and jack 150 to ground. The right hand winding of relay 133 is short^ircuited at this time by the right hand armature and back contact of relay 135. Relay 133 in operating closes at its armature and front contact an obvious circuit for relay 132 which now operates and disconnects the tip of the plug 140 from the operators busy test circuit and completes at the upper arma. tureV and front Contact, the tip conductor for the trunk T. The operation of relay 132 also extinguishes'the guard lamp 109 by the, removing of l@ground at its lower armature and baclr contact. This ground is transferred at the male-before-brealr contact at this armature to the armature of the pulsing relay 126, while the disconnect lamp 136 is connected at this armature to a circuit passing through the armature and back contact o-f relay 104 to the outer left hand armature of relay 110 which relay is, however, operat this time preventing the lighting of this disconnect lamp. Thus, it will be seen that when the plug 140 is inserted in a jack of an outgoing trunk no lamps are lighted at the trunk T.

1f this outgoing trunk to the inward operator l@ at exchange 160 is not busy the tandem toll operator TO transmits the wanted subscribers number to the inward operator TO. As the nature of such trunk lines do not form any part of this invention, the various indications received from the connections beyond will merely be mentioned in so far as they enter in the operation of the trunk T. To fully describe the operations of trunk T under various conditions of the connections beyond it will be assumed that the inward operator at 160 may in one instance connect her plug 162 to jack 163 associated directly with the line of the sub scriber at 161 and in another instance to acl: 164 associated with a second trunk leading to a B operator BO in exchange 165 where this operator may connect the trunk by means of plug 16T to jack 168 associated with the line of subscriber 166.

1f the call is intended for a subscriber 161 the inward operator l0 connects her plug 162 to jack 163, battery will be supplied to relay 126 and a circuit for the operation of ringing lamp 137 will be closed in the following manner: As relay 116 is operated at this tiine,` the operation oft relay-126 causes a circuit for the timing relays 124e and 125 to be closed as Viiollows: batterywinding of relay 12:?,flei'tfhand armature and back contact ci' relay'124f, letthand armature and l'ront Contactl ot 'relay 123, outer lett hand urinature` and lbach contact ot' relay 121, inner right hand arinature and front Contact el relay 116,l armature and i'ro-nt contact ot relay1126v to ground at the nialie-belore-breali contact of relay 132.v A circuit Will also he closed to the' saineA ground lor relay 120 follows:` battery .right hand Winding ot relay `126, innerrighthand armature and bach Contact ot relay 121, normal make-beforelirealz contactsotrelay'122,1iglit hand armature andbach contact of relay 123, inner right `hand armature and bach contact ot relay 116, armature and iront Contact relay 126 to the ground at relay 132.` The operation'ot relay 12() doesv not perfor-ni any useful function at this time Whereas 'the operation ot relay 125 causes the operation ot relay Yfrom battery, Winding et 124, armature and front' contact ot' relay 12.6 over the same path to ground as relay 132. Relay 1241, in operating, breaks the original circuit tor relay 125 atits lettliand armature and' back contact and establishes a locking circuit for' itself at. its lett hand arinature and ont Contact. Thus, is relay 125 prevented ein again operating as long as relay 126 remains operated. A circuit is new est-ahlishe'd by the operation of relay 1211 from the ground at relay 132 for relay 13T as follows: battery Winding of relay 13?, right hand` nialre*before-break contacts oi relay 137` outu er right hand armature and back contact of relay 121, right hand armature and front Contact otrelay 121, inale-betore`-breal contact-of relay 1255 to ground at132 over the saine path as relay 12e;t is operated. rlhe ringing lainp 136 is also operated over this circuit from battery through lamp 138, 1nalie-belore-hreah contactoll relay 137 to ground at relayf132. Relay 137 in operating closes a locking circuit lor itself and for the maintenance ci: lainp 138 lighted at its right hand armature and front Contact directly through the liront Contact and armature of relay 126 to ground at relay 132. The operation of relay 13.7 alsof openslat its inner. lett-hand armature and back Contact, the circuit l'roin the back' lContact of relay 126 to relay 102 to prevent this relay from (nger-ating when relay 126 is later released at the operation ofthe ringing key 1110 as Will be described hereinafter. Relay 116 is nonv also released bythe opening of the outer lett-hand` armature and back contact or' relay 137. rl`his relay can, theretere, not he again energized 'during the a g up ot this connection nor can the ino; circuit ior tiine relays V125 and be again'conipleted through this relay.

to a jack 161 associated with a trunlrleadingv to that other elichangeifl and the operator B@ in this exchange inturn connects the plug 167 of `thisincoining trunk` to jacl; 166 associated with' the Vline ol subscriber 166, battery for relay 126 Will be but inoinentarily supplied at the insertion-oli plug 162 into jed-11165 andf again supplied steadily .when theV li operatorl'B inser s plug 167 in jack 168. This temporary supply battery which operates relay 126 willl not be 0; sufficient duration to light the ringing lainp 138 until the call is completed to the subscribers line 166 `and it' prevented trein operating on this impulse inthe following manner: lielay 116 operated at this .time as hereinbe'lore stated, the lirst opera* tion the relay 126 closes tliesaine circuit as liereinlie'lore described r the operation of relay 125 and this relay in o'icierating closes the circuit :tor relay 1211- Wliicli is sloai toroperate andthe release oi' relay 125 is, therefore, delayed. As relay 125 slow in releasing, the circuit,through the righthand armature and front Contact of relay 124 and through the inalre--belore-brealr Contacts ot relay 125 for relay 137 and lanip is vconsider-ably delayed.` The release oi relay 126 Will', therefore, occur betere this circuit is coinpletedand thus prevent the ringing'- lanip 133 troni operating. rllhis circuit will therefore never be completed as relay 124willv be released immediately upon the' release 'olV relay 126. lloweveig it will be noted that upon the release o1' relay 126, relay 126 will reinain `energized over a cir cuit as-t'ollows: battery right hand Winding ot relay 120, lright hand armatureV and `front contact ot relay 120, `Winding of relay 121, right hand armature and backV contact ol relay 122, right'hand armature and'ibaclr contact ot' relay 11T, lnalie-before-breali coutacts of relay 132 to ground. This circuit will now operate relay 121 `Which did not operate on `this circuit lwhen i'elay126 was operated as it Was` thenV short-circuitefl.by the circuit'through the armature and 'ti-ont contact ot relay 126. lWhen relay 12lfoperates ittransiqers atits outer left hand urinature and front contact the circuit for relays 125 and to -thebaclr contact and arinature ol relay 126. llclay 126 non7 'remains deenergized until theoperator l() insens plug 11?' intojaclr160, and the circuit co-.. pleterl at the haelt contact-ot` this relay will therefore operate the timing relays 124i and lair ing out over the trunk to'release relay 121 and thus restore the counting andrtiming relay arrangement to normal. This action is as follows: Upon the energization of relay 125 and deenergization of relay 124 and consequent release of 125 a circuit is established for the left hand Winding of relay 120, from battery left hand Winding of relay 120, left hand arn'iature and front contact of relay 120, inner left hand armature and back contact of relay 121, right hand armature and front contact of relay 124, make-before-break contacts of relay 125, left hand armature and back Contact of relay 123, outer left hand armature and front contact of relay 121, armature and back contact of relay 126 to ground at relay 132. This circuit through the left hand Winding of relay 120 opposes the circuit through the right hand Winding and causes relay 120 .to release. Upon the release of relay 120, relay 121 also releases thus breaking the energizing circuit for relay 124 Which is thus restored.

Vfhen finally the plug 167 is inserted in jack 168 of subscriber 166 steady battery will be supplied over the trunks back to trunk T and operate relay 126. The opera tion of relay 126 at this time Will of course be long enough to permit the lighting of the ringing lamp 138 in the manner already described in connection with the setting up of a call to a'subscriber 161. It is thus seen that the temporary application of battery to relay 126 will not cause the operation of ringing lamp 138 and connections through several trunk lines and exchanges beyond may therefore be made and the lamp 138 lights as hereinbefore described only at the connection of steady battery when a linal plug of the last trunk is inserted in the acl; of the Wanted subscriber.

At the lighting of ringing lamp 138, the tandem toll operator T() Will ring the Wanted subscriber using a code if desirable. lVhen ringing key 141 is operated audible ringing signals will pass back to the machine switching operatorsposition over co-ndenser's 142 and 143 While the ringing current is golines to the distant city from ringing source 144 and ground at contactV 145. On each operation of the ringing lrey, ground is connected to the right hand locking armature and contact of relay 137 to hold it operated While the ground normally supplied at the front contact and armature` of relay 126 is removed by the release of this relay on the operation of ringing key. Vhen relay 126 releases, a circuit is closed for rela-y 117 as follows: Battery Winding of relay 117, inner left hand armature and front Contact of relay 137, armature and back contact of relay 126 to ground at relay 132. Relay 117 operates on this circuit and supplies at its inner left hand armature and front contact a ground for holding relay 137 operated While the holding ground is removed each time the ringing key is released and before relay 126 has had time to be operated. The ringing lamp 138 is, therefore, maintained lighted during t-he code ringing operations. In case the subscriber does not lift his receiverl from the hook during a code ringing period, it may be repeated as described as the ringing lamp will in this case be maintained lighted at the end of each code ringing period.

It will be noted that each time relay 117 is operated, a path is also completed at its middle left hand armature and front contact for the operation of timing relays 125 and 124 and relay 120. r1`his circuit path serves no purpose unless the subscriber removes the receiver from the hook either during a ringing period or after. In the first case relay 126 will fail to operate at the end of the ringing period and in the second case it will be released the moment the subscriber answers as battery is then removed' from the line. The efl'ect of this release of relay 126 is that the ringing lamp will become extinguished in the following manner: It will be noted that upon the release of the ringing key a ground Will be supplied for the timing relays from battery Winding of relay 125, left hand armature and back contact of relay 124, lefthand armature and back contact of relay 123,

outer left hand armature and bachl contact of relay 121, middle left hand armature and front contact of relay 117, contacts 146 of ringing key 141 to ground. Relay 125 will operate and cause the operation of relay 124 which in turn causes the release of relay 125 as hereinbefore described anda shunt circuit for relay 117 is now completed from the ground at ringing key contacts 145 to the outer right hand armature and back Contact of relay 121 to the battery at the winding of relay 117 which consequently releases. As this relay 117, sup-plies at this time the only holding ground for relay 137 and ringing lamp 138, this relay will release and lamp 138 extinguished by the opening of the inner left hand armature and front Contact of relay 117 when releasing. It will. therefore, be seen thatJ if the subscriber answers and the ringing key is released, ringing lamp 138 will be extinguished as soon as the timing relays 125 and 124 have functioned.

It Will be noted that upon the release of relay 137 and with relay 126 also released, a circuit Will be completed for relay 102 as follows: battery Winding of relay 102. outer right hand armature and back Contact of relay 116, outer left hand armature and back contact of relay 137 armature and back contact of relay 136 to ground at relay 132. lt should be mentioned that relay 116 has already been released as its circuit was Dil ricosfgase opened at the `outer 'left hand armature and bach contact of relay 13T when operated. This circuit therefore operates, as` stated, relay 102 which `opens the shunt tor the lett hand windingoli relay 105 at its leit hand armatureand bach Contact and at its `.inner right hand armature and back cont-act opens the shun-tto resistance 101. The inclusion, of the left hand winding in the `circuit bridging thevconductors 30 oi' the trunk T will cause the release ot relay 28 which removes the ground on the low voltage battery side foi: the resistance 11 and the curren through relay illwill therefore be reversed. This reversed `current will have the ei'liect in theicord circuit A ol1 eritingguishing` a. guard lamp thereat or per-form any other function welll known in the `art to notify` the machine switching operator that the calle(L subscriber has answered. As stated-he resistance 101 for the lett hand windingl of relay 10e will be opened at the operation ofi this relay but relay 10st will not opera-te soo-n on this current as the current inthe right hand winding-oithis relay opposes it, and is still suilicient to prevent this operation. Relay 126 is-released when the called subscriber answers 'and conversation may now begin between the subscriber at 10 and the subscribi-5i'l` at 161 or 166, whichever subscriber is connected.` 4For the salie of review of the situation up to this time, it may be mentioned that during the talking period, relays 105,106, 110,102, 132, is, ai and 27 are operatedand all lamps are extinguished.

' When the called subscriber replaces his receiver on the hook, relay `126 is again energized causinv` the circuit tor relay 102 to be broken atl the armature and back contact of relay 126. The release of relay 10'2 restores the shunt circuit around the lett hand winding of relay 105 which in turn causes relay 28 to become operated and restore the ground on the low voltage batteryside of resistance 11 and thus again cause the reversing of the current to the line at the `machine switching` operators position where the proper disconnect guard lamps or signals are again lighted indicating that the called subscriber has disconnected. It will be noted that the disconnect lamp 136 at the tandem toll operators position TO is not lighted at this time but as soon asthe machine switching` operator disconnects, Aground is removed-troni the sleeve lead the brush 26 and terminal 25 so thatA relay 21 is now released and the release of this relay opens the circuit from `the high voltage batter; through the resistaneell to the left hand winding' or" relay 14. `Relay 21 also opens the circuit for relays 27 which on releasing' opensthe circuit for relay 12 which,ihow ever, releases slowly to permit the relays in the -eord circuitto function and releases the switch 20.y Relay 21 also opens the circuit from the high voltage battery at rclay 28 thus causing the release of relay 105 which in turn causes the release of relay106 andthe release of relay 110. The release ot relay 110 closes the circuit for the disconnect lamp 136 as follows: battery lamp136, lower armature and front contact of relay 37, armature and back contact of relay 10st, outer armature and back contact oiwrelay 110 to ground.

machine switchingl operator has released.

It should be noted that a parallel branch of the circuit that operates lamp 136 operates relay 135. The operation of relay 135 opens the shunt circuit -for the night hand winding oll relay 133. Relay 133, however, does not release but the decreased currentfin this circuit causes a sleeve relay in the trunk circuit beyond to release and send the proper disconnect signals to the distant station as is well known in the art. The tandem toll operator now remove-s the plug 140 from jack 150v and relays 133, 132 and 135 are consequently released and lamp extinguished.

If the machine switching operator should disconnect before the called subscriber, the circuits function in the same manner to light-the disconnect lamp 186; i. e., the relays 21, 2?, 1Q, E38, 105,V 106 and 110 willrelease in succession causing the lighting of lamp 136 and operaJion of relav 165.

It both the machine switching; operator and the called subscriber should disconnect` simultaneously, the operation is also the same and it might be mentioned herethat the circuit for relay 126 is opened at the left hand armature and back contact of relay 135. This is for this relay 136 from shuntinp; the corresponding relay in Vanother trunk circuit that may, in the meantime, i. e., between the liirl'iifino; of' the disconnect lamp 136 and the removal of plus; 14A, have been connected to a jack in multiple to jack 150 of the same outgoing; trunk. l

IfV the machine switchingoperator releases the trunk T before the wanted subscriber has answered, the relays Q1, 27,12, 255, 105, 106 and 110 are released in the same manner as hereinbeiore described and the disconnect lamp is lighted.

ln case the machine vmviichine' operator desires to call the tandem toll operator beiore` the wanted subscriber has answered, she operates a'tlashingj hey such 8 in the cord circuit which disconnects relay 9'and reverses the line battery causing the operation of relay 1li in' the trunk circuit. llpon the operational' key 8 each wind'ngr otrelav let is included in a separate circuit troni g rand to batt Those two circuits are l to each o r in all respecte save the resistance oi 'the windings or' relay la.

Lamp 136 when lighted in` dicates to the tandem toll operator that the the purpose of preventing' l Therefore different currents will tiow in these two windings and since the number of turns in each is the same the magnetic effects will be different and though opposed to each other there will be a resultant sufiicient to operate the relay. The operation of relay 141 closes the obvious circuit for relay 31 which causes a reversal of current over the conductors 30 for relay 105 as follows: high voltage battery, winning of relay 28, inner left hand armature and front contact of relay. 21, resistance 29, right hand armature and front contact of relay 31, upper right hand winding of repeating coil 15, left hand -armature and back contact of relay 102, right handwinding of relay 105 to a point 103. From t-his point 103 in two parallel circuits, one through the left hand winding of relay 104, another through the inner right hand armature and back contact of rela-y 102 and resistance 101 and from there through inner left hand winding of repeating coil 175 to the ring conductor of the trunk T, loweil right hand winding of repeatingy coil 15, left hand armature and front contact of relay 81, resistance 82 to ground. Relay 105 is there by released but immediately energized again at the release of the flashing key at the machine switching operators position and thus follows the pulses of this flashing key. However, the rate at vwhich this key is operated prohibits the release of relay 106 which is slow to release while the reversal of the originally applied battery causes the operation of the polarized relay 104. This relay closes every time it is operated at its armature and front contact a circuit for the auxiliary signal 108 and line lamp 109 as follows: battery, line lamp 109, normal contacts 181 of listening key 112, outer left hand armature and front contact of relay 110, armature and front contact of relay 104, auxiliary signal 108 to ground. These signals are therefore, flashed in accordance with the operation of the flashing key to notify the tandem toll operator that the machine switching operator desires to communicate some further information. The fact that relay 106 does not release will naturally maintain the relay 110 operated and thus prevent the disconnect signal from operating.

1f the machine switching operator flashes the tandem operator after the subscriber has answered, the operation is the same except that relay 102, is operated. This, however, merely opens the shunt circuit for the left hand winding of relay 105 and the shunt circuit through resistance 101 for the left hand winding of relay 104C which has no effect on the operation of this relay in response to the flashing operations.

In case the wanted subscriber desires to call the machine switching operator, he manipulates the switchhook which causes the opera-tion of relay 126 each time the switchhook is depressed. The operation of relay 126 causes the release of relay 102 which shunts the left hand winding of relay 105 which in turn causes the release of relay 28 reversal of battery and the corresponding operation of a supervisory lamp at the machine switching operators cord circuit each time the switchhook is depressed as hereinbefore described.

' In case the machine switching operator, after having released, again connects with a trunk T in response to a call from another subscriber before the trunk T has been released by the tandem toll operator from the connection beyond and the relays in this trunk circuit have not been restored to normal, the line lamp 109 and auxiliary lamp 108 will be lighted in addition to the disconnect lamp 186 which remains lighted until the tandem toll operator removes plug 140 from the outgoing line jack. These lamps are lighted by the reoperation of the relays 105 and 106 as in the setting-up of an ordinary connection while the disconnectlamp will remain operated as long as relay 132.is operated and the fact that relay 110 is in normal posit-ion; i. e., before the listening key 112 has been operated a second time which will not occur until after the tandem toll operator removes her plug 1410 from the circuit beyond. The disconnect lamp 186 will naturally be extinguished in either case.

If, after the tandem toll operator has inserted her plug 140 in jack 150 or 170, it is found that the inward operator TO, the B operator BO, the inward operator IBO or the wanted subscriber at any of these points is found busy, so-called busy back signals are sent to the trunk T. These signals are transmitted to the machine switching operator at A without. operating the ringing signal in the trunk T or in any other way disturb or interfere with the condition of the connection extended to the busy point. These busy back signals which are direct current impulses should, of course, be of such frequency as not to be confused with the temporary impulses caused by the extension of the connection to the several trunk lines and exchanges nor should they cause the operation of the ringing lamp 188, yet be capable of producing indications at the machine switching` operators positions which are to be interpreted by them as busy signals. To produce this effect, the busy back pulses operate and release relay 126 at a certain frequency and the first pulse received operates relay 126 to prepare the following circuit: battery, right-hand winding of relay 120, inner right-hand armature and back contact of relay 121, makebefore-break contact of relay 122, righthand armature and back contact of relay 123, inner rightdiand armature and back contact of relay 116, armature and front Ill) contact of relay 126, to ground at relay 1212. A circuit is also closed for the tiining relays as follows: battery, winding of relay 125, left-hand armature and bach Contact of relay 124, left-hand armature and bach contact of relay 133, outer left-hand armature and bach contact of relay 121 to ground at relay 132 the saine as the circuit previously traced. The operation of relay 125 causes the operation of relay 124C as herein before described and the operation of relay 121 causes the release of relay 125 and the extension of the circuit for the ringing lanfip 138, but the functioning ofzthese two relays 121L and 1253 occupies suilicient time to prevent this circuit through the ringing lamp being completed before the busy bach pulse has ceased and relay 126 released. Relay 120, in operating, closes a circuit for relay 121 to ground at relay 132, but this relay does not operate until relay 12o releases, at which time it transfers the circuit from the timing relays to the back Contact of relay 126 which causes these relays to release and become again energized, whereas, relays 120 and 121V are held up through this circuit from battery, right-hand winding of relay 120, riglithand armature and front con.- tact of this relay, winding of relay 121, right-hand armature and baci; Contact of relay 122, right-hand armature and back Contact of relay 117 to ground at relay 132. The time relays do not, however, have time to extend the circuit through the inner lefthand armature and front contact of relay 121 before relay 126 is again operated at which time` they are again released. Relay 121 prepares a circuit for relay 122 so that when relay 126 is again operated, a circuit for this relay is completed from battery winding of relay 122, inner right-hand ar- Amature and front Contact of relay 121 1nalrebeforebrealr Contact of relay 122, right-hand armature and baclr contact of relay 128, inner right-hand armature and front contact of relay 116, armature and iront Contact of relay 126 to ground at relay 132. Relay 122, in operating, prepares a locking circuit for itself from the ground at relay 132 over its left-hand armature and front contact. Relay 122 in operating, brealrs at its rio'hthand arn iture and back contact the holding circuit for relays 120 and 121 which are now released and also prepares at its contact 116, a circuit for re lay 123 which, however, is shunted as longv as relay 126 is operated. is relay 126 agen the second impulse this cirreleases after cuit for relay 123 is effective and relay operates from battery, winding of relay 122, left-hand armature, front contact and con tact 176, winding of relay 123, inner righe band armature and bach contact of relay 11Tl to ground at relay rlie operation of relay 123 now prepares a circuit for relay 102 so that when relay 126 again 0perates on the third nnpulfife, 'slay 102 1s energized as l y ffllows: battery, win ling of relay 102, ri t contact `f rut-hand ifiinature and fron' of rei. 1223, inner right-hand r- 70 mature inature and front Contact of relay 11T, ar

and front Contact of relay 126 to ground at relay 122. The opetion of relay 102 causes a supervisorT signal to be lighted to signal the machine switching operators position as hereinbefore described and the following restoration of relay 12S causes relay 102 to be released which consoquently also ertinguiehes the lainp at the machine switching operators position. lle lays 122 and will nonv be held up until the tandem toll operator fl reinoyes the plug of trunk T from the outgoing jacl. The following or fourth busy bach irfipulse in operating relay 126 causes this lamp to be again operated that is, this lan'ip will flash in response to the followino impulses. During this whole operation, if as is the case in saine equipments there is any audible busy tone placed on the circuit, it is pass d through the condensers 1112 and 113 of the trunlr T and tnnsinittod to the niaehine switching operators telephone set in the usual manner if it is connected at this tiine to the cord circuit. @he will, therefore, in 9v this case receive the first two impulses of busy baci; tone before the supervisory lainp lights on the busy back pulses.

What is claimed is:

1. In a telephone system, a trunl; circuit comprising signals, ineens for operating said signals when the trunk is seized, an operators telephone set, a hey for connecting said telephone set to the trunk, and means actuated when the hey operated for disabling said signa-ls and when the key is released for again operating one of said signals only.

2. ln a telephone systein, a trunk circuit comprising` a plurality of signal lamps in a common circuit, a rela" llO operated when L o trunk circuit is seized for closing the cli cuit to light the signal lainps, a hey, a second relay, and circuit lneans whereby the actua tion of the hey causes the operation of the relay to entinguish the signal lainps ai i whereby the sibsequent ease of the lrey causes the re-lighting of one said signal lamps.

In a telephone system, a 'unit circuit, an operators position at the incoming of said trunl; circuit for signals in said trunk circai4 means for operating said trunk is seized at the outgoing end, and ineens for disabling said nils when the trunk seized b f the op." l' and re-oi., ating` one of said signals when a trunk is released by the operator.

er. ln a telephone system, a trunk circuit,

an operators position at the incoming end of said trunk circuit tor seizing the saine, signals in the trunk circuit at said position, means for extending said trunk circuit at the incoming end, means tor operating said signais when a trunk is seized at the outgoing end, means for disabling the signals when the trunk is seized by the operator and reoperating one of said signals when the trunk is released by the operator, and means toi.' disabling said re-operated signal when a trunk line is extended at the incoming end.

5. ln a telephone system, a trunk circuit comprising signals, means for operating said signals when the trunk is seized, a key, means tor disabling said signals when the key is operated and re-operating one of said signals when the key is released, and means for disabling said re-operated signal when the trunk circuit is extended.

6. In a telephone system, a trunk circuit, means for connecting said trunk circuit to a wanted subscribers station, a signal operated when a wanted subscribers line has been connected with said trunk circuit, a key in said trunk circuit, a source of current connectedV by the actuation ot the key in the trunk circuit Jfor ringing the seized subscribers sta tion, and means in said trunk circuit controlled by the operation of the key 'for maintaining said signal operated during the operation of the key and until the Wanted subscriber answers and the key is released.

7. In a telephone system, a trunk circuit comprising a signal, means operating said signal when battery is supplied to the trunk circuit, a key for controlling said operating means to maintain the said signal operated when the key is actuated to remove the battery supply from said signal operating means and means tor disabling said signal when the key is released and the battery is removed from the trunk circuit.

8. ln a telephone system, a subscribers line, a trunk circuit adapted for connection with said subscribers line comprising a signal responsive to the connection of said trunk circuit with said subscribers line, a source of' ringing current, a key for transmitting ringing current to the subscriber on said line, means responsive to the actuation of the key for maintaining said signal operated While ringing current is transmitted, means :tor disabling said signal when the key is returned to normal position and when the subscriber answers tlie call.

9. InV a telephone system, a subscribers line, a trunk circuit adapted tor connection with said subscribers line comprising a signal, means 'lor actuating said signal responsive to the connection ot said trunk circuit with said subscribers line, a source ot ringing current, a key tor transmitting ringing currents to call the subscriber on said line, and means for transferring the control over said signal trom t-he means for actuating it to the key to maintain the signal actuated when the key is actuated and to disable the signal when the key is restored it the subscriber on the siezed line has answered the call.

10. ln a telephone system, subscribers lines, a trunk circuit adapted for connection with any one of said lines and comprising a signal, means :tor actuating said signal re sponsive to the connection of trunk circuit with a subscribers line, a. source of ringing current, a key tor transmitting ringing current to call the subscriberron said seized line, means Voperative when said key is actuated to transmit induced ringing current to the out-going end ot said trunk line, means for transferring the control over said signa-l from the means tor actuating it to the key to maintain the signal actuated when the. key is actuated and to disable the signal when the key is released it the subscriber on the seized line answers the call, and means tor transmitting a signal indication to the outgoing endof said trunk line when the key is released and the subscriber answers.

11. ln a telephone system, a trunk circuit comprising a signal, means operating said signal when battery is supplied at the incoming end of said trunk circuit ier a certain period, a key tor controlling said operating means to maintain said signal operated independent of said battery supply, means for returning said signal operating means under control of said battery supply it the key is returned to normal and tor disabling the signal it the battery is removed, and means for establishing a signal indication at the outgoing end of the trunk circuit when the signal is disabled.

12. ln a telephone system, a trunk circuit comprising a signa-l, ,means operating said signal when battery is applied at the incoming end of said trunk circuit ior a certain period, a key for controlling said operating' means to maintain said signal operated independent ot said battery supply, means for returning said signal operating means under control of said battery supply if the key is returned to normal and tor disabling the signal it the battery is removed for a certain period and means for establishing a signal indication at the outgoing end of the trunk circuit when the signal is disabled.

13. In a telephone system, a trunk circuit Vcomprising a signal, means tor operating said signal it battery is applied at one end of said trunk 'for a certain period ot time. and means for disabling said signal and for transmitting signal indications to the other end of said trunk circuit it battery is removed tor a certain period.

14.-. In a telephone system, a trunk circuit comprising a signal, means for operating said signal when battery is supplied at the outgoing end of said trunk circuit for` a cerfluo tain period, means for preventing said signal operating means from operating if battery is applied to said trunk circuit for shorter period, means for transmitting nal indications to the outgoing end of said trunk circuit if battery is applied at the incoming end of the trunk circuit in impulses of a certain duration and at a cert-ain interval ot time between said impulses provided that at least three impulses have been received.

l5. In a telephone system, a trunk circuit comprising means for completing a circuit in said trunk circuit if battery is supplied for a certain period and means for preventing said circuit from being completed and for completing another circuit in said trunk cir-- cuit at the third in pulse o1 battery it said impulses are supplied at a certain frequency.

1G. In a telephone system, a trunk curcuit comprising tivo circuits, means for completing one ci said circuits if battery is supplied to said trunk circuit ior a certain period and for preventing it 'from being completed and for completing the other circuit on the third and each succeeding impulse of battery if said impulses are supplied at a certain frequency.

l?. In a telephone system, a trunk circuit comprising tivo circuits, means for completing one of said circuits if battery is supplied to said trunk circuit for a certain period, and means for preventing said circuitfrom being completed and for completing the other circuit when battery is supplied in impulse of shorter duration after said impulses have occurred at least three successive times at a certain frequency.

18. In a telephone system, a trunk circuiti comprising tivo signaling means, a relay, means for completing a ciicuit :for the operation ol one of said signaling' means: if said relay remains operated a c^rtain p riod or' time. and means for completing another circuit for the operation of the other signaling means if said relay is operated a certain number of times When the periods of operation are of shorter duration.

i9. In combination, a relay, a circuit operated thereby, and a time relay arrangement for ext-ending said circuit in one direction it said relay is operated a certain period of time and for extending said circuit in another direction if said relay is operated a certain number of times in succession the circuit being extended each time said relay is operated after the first tvvo operations of said relay.

20. In combination. a relay, a circuit operated thereby, a time relay arrangement ior extending said circuit in one direction if said relay is operated a certain period of time. and a counting relay arrangement cooperating With said time relay arrangement to prevent the extension of said circuit in said direction and for extending it in another ciircction it' said relay is operated a certain number of times in succession provided the periods of operation or the relay are shorter and occur at a certain frequency.

2l. In combination, a relay, a circuit operated thereby, a time relay arrangment for extending said circuit in one direction if said relay is operated a certain period of time, a c unting relay arrangement cooperating with said time relay arrai'igemei'lt prevent the extension of said circuit in said direction and for extending it in another direction it said relay is operated a certain number of times in succession provided the A eriods of operation ot the relay are shorter and occur at a certain 'iraquencl and means for thereafter closing d circuit in the second direction each time the relay is operated.

In a telephone system, a trunk circuit comprising a signal, means for operating said signal if battery is supplied to said trunk circuit for a certain period and for disabling said signal if battery is removed any time after said period has elapsed, and` means operative when the signal is disabled for preparing a circuit that may be completed any time thebattery is thereafter removed Jfrom the trunk circuit.

23. In a telephone system, a trunk circuit comprising a signal, means for operating said signal if battery is supplied to said trunk circuit for a certain period of time, means for disabling said signal if battery is removed after said period of time has elapsed, and means operative to transmit a signal indication each time battery is thereafter removed.

24. In a telephone system, a trunk circuit comprising a signal, af relay, a time relay arrangement for operating the signal if said relay is held operated for a certain period,

a circuit, a relafy arrangement for disabling said slgnal and completing said circuit When said relay is released, means lor breaking said circuit each time the relay is thereafter operated and completing it each time the relay is thereafter released.

25. In a telephone system, a trunk circuit comprising a relay arrangement, a1 disconnect signal, means for operating` said disconnect signal ii the trunk circuit has been extended and said relay arrangement is released by the removal oil a battery supply of one polarity, other signals, means for repeatedly operating said other signals Without operating said disconnect signal it the trunlr has been extended and said relay arrangement is released by the removal ot this polarity of battery and alternately operated by the other polarity of battery at a certain frequencyl 26. In a telephone system, a trunlr circuit comprising a disconnect signal, other signals,

loo

means for operating the disconnect signal it said trunk circuit is extended and battery ot one polarity is removed from said means, and means ior operating the other signals each time battery of the other polarity is applied in momentary alternate impulses to said two means and the trunk circuit is extended.

27. In a telephone system, a trunk circuit 'comprising a disconnect signal, other signals, means for operating the disconnect signal if said trunk circuit is extended and battery ot' one polarity is removed Jfrom said mean-s, means for transmitting a signal indication to the extended end of the trunk circuit simultaneously With the operation ot' the disconnect signal, and means for operating the other signals each time battery oil the other polarity is applied in momentary alternate impulses to said iirst and last mentionecL means and the trunk circuit is extended.

Q8. ln a telephone system, a trunk circuit comprising a disconnect signal, means for operating said disconnect signal it the trunk is extended and battery is removed from said means, other signals, and means for operating said other signals Without disabling the disconnect signal if the trunk line is extended and battery is again supplied to said first mentioned means.

29. In a telephone system, a trunk circuit comprising a relay arrangement, a disconnect signal, means for operating said disconnect signal it' the trunk circuit is eX- tended and battery is removed from said relay arrangement, other signals and means for operating said other signals it the trunk circuit is extended and the disconnect signal has been operated if said battery is again applied to said relay arrangement Without. disabling the disconnect signal.

30. In a telephone system, a trunk circuit comprising a disconnect signal, means for operating said vdisconnect signal it the trunl; is extended and battery is removed from said means, other signals, means Jfor operating said other signals Without disabling the disconnect signal if the trunk is extended and battery is again supplied to said iirs mentioned means and means for disabling said disconnect signal without disabling the other signals when the trunk becomes disengaged.

ln Witness whereof, I hereunto subscribe l my name this 5th day of May, A. l). 1924.

LANGFORD J. BOWNE. 

